There are many systems that have a backup supply in the form of batteries, generators or other UPS sources. Some power systems, for example, include rectifiers that receive and rectify AC power to produce DC power on a bus for powering external equipment (i.e., loads). When the AC source is unable to provide power, power systems can utilize batteries as back-up to provide DC power on the bus. In some systems, the battery reserve can be highly undersized and subjected to a very high rate of discharge for a short period of time. To prevent damage to the batteries or shortening their useful life, batteries are actively disconnected from the DC bus. Not only does this help the batteries it prevents damage to cables and other system components.
Traditional low voltage disconnect (LVD) schemes in the Telecom industry utilize a pure voltage disconnect threshold or a combination of a voltage or elapsed time disconnect threshold. These traditional methods of disconnect, however, are not optimum for Very High Rate (VHR) discharge applications. In VHR discharge applications, the discharge times are generally less than a minute with a 10-15 second reserve design time being very common. Traditional disconnects are not optimum because these disconnects are for systems designed for longer reserve times that can range from one-to-eight hours or more. The algorithms associated with traditional disconnects are tailored for battery reserve systems designed for sustained deep discharges. Thus, battery life and system reserve time can be at stake when using traditional LVD schemes with VHR discharge applications.